The present invention relates to a process for casting a metallic melt into a continuous casting mold.
When casting a steel melt, for example, from a tundish or a distributor into a continuous casting mold, it is a common practice to use a sliding closure unit or slide gate as a controlled valve for controlling the quantity of melt discharged per unit of time. In this case, the slide gate normally operates in a variable throttling position, that is, in a position throttled over half of the possible full opening so as to enable it to follow the opening and closing commands that emanate--in the case of an automatic control of an adjusted set level of the melt in the ingot mold--from a control system which obtains data from a sender and receiver used to detect the melt level in the mold. A constant pull-off rate is established so as to improve the strand quality of the cast steel. In this case, it may come to pass that an imbalance occurs between the quantity of melt being discharged from the tundish and the strand stock emerging from the ingot mold that can no longer be compensated for by the slide gate. This is attributable to a narrowing of the opening of the flow channel.
Such a narrowing of the opening can occur, for example, during the casting of aluminum-killed steels, wherein aluminum oxide is deposited in the flow channel, mainly on the throttling edges of the movable plate of slide gate, thereby clogging the opening thereof. Likewise, the flow channel can be clogged by the freezing of the melt when the channel wall has not yet been heated adequately in the initial phase of the casting process. Heretofore, such a narrowing of the opening that is building up has been compensated for by appropriately opening the movable plate of the slide gate until it reaches its fully open position and, optionally, by reducing the pull-off rate of the cast strand to a lower limit that is still acceptable from the metallurgical point of view. Thereafter, it is necessary to terminate the casting operation, which can lead to considerable difficulties and costs.